I've been having brake bleeding issues since Thursday, wondering if anyone can shed some light.

I removed an aftermarket BBK off the car and reinstalled the OEM calipers then proceeded to bleed 12 hours later.

I've circulated nearly 2 gallons of brake fluid through the system, using a Power Bleeder, the Two Man Method and a Vacuum Pump. Got some air out, but the pedal still goes right to the floor. Yes, I'm using the MC>farthest>closest>MC method.

I had a Mazdaspeed strut tower bar with MC brace installed on the car for a good long while (All bleeding was done with it off). I once over tightened the MC brace, which actually caused brake drag and brought the car to a complete stop that I couldn't get out of no matter how much I tried to accelerate.

I was thinking that perhaps during that incident or after a fender bender I could have done some permanent damage to the piston inside the MC, and if so is there a way I could fix that?

Next step is to rebrace the MC and see if I can get additional air out of the system.

 

If the piston inside the MC is damaged your out of luck. A new MC is needed. A shop will not hone and replace an aluminum MC (if thats what we have). And most will not take the risk on a steel MC either.

Question. Did you let the MC resovoir empty when changing calipers? If so you need to bench bleed the MC. If there is air in the MC it will not be bled out without bench bleeding.

 

I did not fluid level was kept at near full during Two Man and Vacuum bleeding.

 

...could you possibly have an air leak with the removal of the BBK and reinstall of stock? ...smthg not quite tight, or stripped or cracked....? That's would keep you pumpin for a long while.

...and do you ever get a stiff pedal at anytime during the process? Or does it just go to the floor even when you close a bleed valve?

 

I would see fluid leaking out if it were anywhere to do with the brakes would I not? I will try some soapy water on the bleeder screws and brake line hose connections to be sure.

Where could I suck air but not shoot fluid.....? (o boy)

 

Easy. If you bleed screw is loose, worn, or the thread has spread too large, that sort of thing, it will suck air in every time you release the pedal, then force it out when you push down again.

But back to basics, you mean to say if all bleed screws are tight, and the last bleed is the MC, and everything is buttoned up tight, your not leaking any fluid......your pedal still goes to the floor? If yes, then you've got a MC issue.

 

how many miles on your 8?

When two man bleeding was the pedal pushed all the way to the floor?

 

Also best (when doing two man method) to have the car running when you do the bleed and press the pedal slowly and release slowly...BTIM not a stomp and release.

 

I think we're on the same track. Sounds as thought the MC piston cups (seals) are worn/deformed during the bleeding.

 

64,000

The pedal goes to the floor initially. When you depress and release a few time it gets firm, leave it alone for 30-60 second gets soft again (o boy). Just feels like Air in the Lines!

Hummm I've always done it with the car off, pump the pedal 3 times then hold it as the bleed screw is opened, then depress?

 

Just torqued the MC brace on the mazdaspeed bar on the MC again, as i did it the MC made a quiet gurgling noise..... stay tuned. (waiting for the second man to arrive)

 

If you leave the system open for a long time as you did then the fluid drains downward and air upward through the system

no, you don't have to bench bleed the MC, that's what the bleed nipple is for

no the car doesn't need to be running, never even heard that loo-loo before

apparently nobody bothered to read the service manual, particularly the caution note under item #7 for the MC reoval/install procedue:

"... if air still exists in the brake lines even after bleeding the brakes, brake drag occurs, orother malfunctions are present, it is possible that the MC piston is jammed against the pushrods retainer of the power brake unit. If air cannot be bled completely, brake drag exists, or other malfunctions occur, remove the MC and reinstall it properly"

so I'm not sure but it's possible that the brace etc situation may have caused this issue. I'd try to do it without breaking the lines if possible

 

Here's a possibility..something you might have done by tightening the MC brace. It may have torqued it at an angle so you might not get a good bleed anymore.

 

Yep that's where this hypothesis came from.

When you do that how much fluid do you loose? Example if I top off the MC then open all the caliper bleed screws will the MC be drained after 3-6-12 hours?

 

After extensive loop/bench bleeding of the MC bleed screw, I've managed to re-engage the brakes but they are still very very soft...... I can depress the pedal fully while moving the car and it will gradually decelerate. Team could you answer my gravity bleed question?

 

It will drain, you can even gravity bleed your brakes that way by leaving the bleed screw open.

I have no idea how much it potentially could fully drain any open line at a minimum

if the MC isn't vertical it should be obvious, the dragging or jammed piston not so obvious


.

 

Would it be better to open the furthest calipers bleed screw, furthest plus MC bleed screw, all the calipers bleed screws, all the calipers plus MC bleed screw .... ?

Basically, I just wanna know how frequently I'll have to top off the fluid as to not introduce more air into the lines...?

 

Just keep the MC reservoir from going low and allowing air into the system

 

I getcha, just looking for a "set it and forget it" kinda method.

 

Ding ding ding, we have a winner. Wish I would have known before I let all that air into the system hooking up the OEMs, woulda saved me a $300 bucks or so.

 

Another method I have used is:

If the brakes work partially with a pump, drive it around the block.

Go slow stop several times.

This shakes up the air and helps it escape on the next bleeding session.

I've had persistent air in the lines before.

Sometimes it takes a couple of weeks to get the air out.

Drive it and bleed it on the week end.

 

we'll never know what really happened ....

 

I posted what the issue was, deformed MC seals, had to buy a new MC from Mazmart.

 

I've been wrenching on cars for 34 years and this is the first case I've ever heard of a MC being perfectly fine up until a brake bleeding, upon which it then failed catastrophically

 

Could be that it was perfectly fine dealing with fluid, but when a massive amount of air was introduced into the system hooking up the OEM Calipers it couldn't do the job....?